KR100832070B1 - GaN type light emitting diode device - Google Patents

Abstract

The present invention relates to a gallium nitride-based light emitting diode device, the substrate; An n-type gallium nitride layer formed on the substrate; An active layer formed on a portion of the n-type gallium nitride layer; A p-type gallium nitride layer formed on the active layer; A transparent conductive film formed on the p-type gallium nitride layer and having a plurality of intaglio irregularities spaced a predetermined distance therein; A p-type electrode formed on the transparent conductive film; And an n-type electrode formed on the n-type gallium nitride layer on which the active layer is not formed.

LED, light extraction efficiency, transparent conductive film, intaglio irregularities

Description

Gallium nitride based light emitting diode device {GaN type light emitting diode device}

1 is a perspective view showing the structure of a gallium nitride-based LED device according to the prior art.

2 is a perspective view showing the structure of a gallium nitride-based LED device according to a first embodiment of the present invention.

3 (a) and 3 (b) are plan views illustrating current flow control according to an arrangement of intaglio irregularities of a gallium nitride based LED device according to a first embodiment of the present invention.

4 is a plan view for explaining the current flow control according to the size of the intaglio irregularities of the gallium nitride-based LED device according to the first embodiment of the present invention.

Figure 5 (a) and (b) is a photograph showing the appearance and light emission state formed by the intaglio and embossed concave-convex of the same size.

6 is a cross-sectional view showing the structure of a gallium nitride based LED device according to a second embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

110 substrate 120 n-type gallium nitride layer

130: active layer 140: p-type gallium nitride layer

150: transparent conductive film 150a: intaglio irregularities

160: n-type electrode 170: p-type electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride based light emitting diode (LED) device, and more particularly, to improve the external quantum efficiency of the device and to improve the electrical and optical characteristics. The present invention relates to a gallium nitride based LED device.

In general, LED is widely used as a display light source having features of small size, low power consumption, high reliability, and the like, and the material of LEDs that have been put into practical use is group III-V such as GaAs, AlGaAs, GaN, InGaN, and AlGaInP. Compound semiconductors using nitrides are used, and light sources such as red, yellow, and green may be formed by changing compound semiconductor materials to realize various colors of light.

On the other hand, the efficiency of light generated in a gallium nitride-based LED device is divided into the internal quantum efficiency and the external quantum efficiency, the internal quantum efficiency is determined by the design and quality of the active layer, in the case of the external quantum efficiency light generated from the active layer It is determined by the degree to which the gallium nitride-based LED device comes out.

Hereinafter, a structure of a gallium nitride based LED device according to the related art for improving external quantum efficiency will be described in detail with reference to FIG. 1.

1 is a perspective view showing the structure of a gallium nitride-based LED device according to the prior art.

Referring to FIG. 1, in a conventional LED, a sapphire substrate 110, a buffer layer (not shown), an n-type gallium nitride layer 120, an active layer 130, and a p-type gallium nitride layer 140 are sequentially grown. A portion of the p-type gallium nitride layer 140 and the active layer 130 are removed by etching to expose a portion of the n-type gallium nitride layer 120.

On the p-type gallium nitride layer 140, a transparent conductive film 150 having embossed irregularities having a predetermined shape is formed on a surface thereof. The embossed irregularities are typically formed by etching an upper portion of the transparent conductive film 150 by a predetermined thickness.

The n-type electrode 106 is formed on the exposed n-type gallium nitride layer 120, and the p-type electrode 170 is formed on the transparent conductive film 150.

The LED element as described above operates as follows.

Holes injected through the p-type electrode 170 are laterally enlarged in the p-type electrode 170, are injected into the active layer 130 from the p-type gallium nitride layer 140, and the n-type electrode 160 is formed. The injected electrons are injected into the active layer 130 from the n-type gallium nitride layer 120. In addition, holes and electrons are recombined in the active layer 130 to emit light. This light is emitted to the outside of the LED device through the transparent conductive film 150.

At this time, in the structure of the conventional LED element as described above, the angle from the normal to the interface between the flat portion and the air is the critical refractive angle of the transparent conductive film 150 by embossed irregularities formed on the surface of the transparent conductive film 150 Even in the case of larger light, the incident angle may be smaller than the critical refraction angle when incident on the portion in which the relief is formed. Therefore, the probability that light generated in the active layer 130 is emitted outside the LED device without total reflection is increased, and thus, the external quantum efficiency can be improved.

By the way, in the conventional LED device, as shown in Figure 1, when forming a projection embossed concave-convex on the surface of the transparent conductive film 150, the upper portion of the embossed concave-convex, that is, the transparent conductive film 150 Since the upper surfaces of the) are separated from each other without being connected to each other, the current applied from the outside through the p-type electrode 170 is substantially lower than the portion of the entire thickness of the transparent conductive film 150 except for the portions where the unevenness is formed. It will flow only to the area corresponding to the thin thickness of.

In this case, since the sheet resistance (Rs) of the transparent conductive film 150 is increased, it is difficult to improve the overall light emission efficiency, such as the operating voltage of the device is increased and the light emission is concentrated at the periphery of the electrode.

That is, in the related art, in order to improve the external quantum efficiency, there is a problem in that electrical and optical characteristics of the device are deteriorated by embossed irregularities formed on the surface of the transparent conductive film.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a gallium nitride-based light emitting diode device that can improve the external quantum efficiency of the device, and also improve the electrical and optical properties. .

A gallium nitride-based LED device according to a first embodiment of the present invention for achieving the above object, a substrate; An n-type gallium nitride layer formed on the substrate; An active layer formed on a portion of the n-type gallium nitride layer; A p-type gallium nitride layer formed on the active layer; A transparent conductive film formed on the p-type gallium nitride layer and having a plurality of intaglio irregularities spaced a predetermined distance therein; A p-type electrode formed on the transparent conductive film; And an n-type electrode formed on the n-type gallium nitride layer on which the active layer is not formed.

In addition, a gallium nitride-based LED device according to a second embodiment of the present invention for achieving the above object, the substrate; An n-type gallium nitride layer formed on the substrate; An active layer formed on a portion of the n-type gallium nitride layer; A p-type gallium nitride layer formed on the active layer and having a plurality of intaglio irregularities spaced a predetermined distance therein; A transparent conductive film formed on the p-type gallium nitride layer; A p-type electrode formed on the transparent conductive film; And an n-type electrode formed on the n-type gallium nitride layer on which the active layer is not formed.

Here, the intaglio irregularities are arranged at least on the shortest distance between the p-type electrode and the n-type electrode.

In addition, the size of the intaglio unevenness is characterized in that it becomes smaller gradually from the shortest distance between the p-type electrode and the n-type electrode toward the outer portion of the substrate.

In addition, the intaglio irregularities are characterized by having a planar shape of a circle or polygon.

In addition, the p-type gallium nitride layer and characterized in that it further comprises a p + gallium nitride layer formed between the transparent conductive film.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like parts throughout the specification.

Now, a gallium nitride based LED device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment

First, the gallium nitride based LED device according to the first embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5.

2 is a perspective view showing the structure of a gallium nitride-based LED device according to a first embodiment of the present invention.

As shown in FIG. 2, the gallium nitride based LED device according to the first embodiment of the present invention includes a buffer layer (not shown), an n-type gallium nitride layer 120, an active layer 130, and the like on the substrate 110. The p-type gallium nitride layer 140 is sequentially stacked.

The substrate 110 is preferably formed using a transparent material including sapphire, in addition to sapphire, zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC) ) Or aluminum nitride (AlN).

The buffer layer may be formed of GaN, which may be omitted.

The n-type or p-type gallium nitride layers 120 and 140 may be formed of GaN layers or GaN / AlGaN layers doped with a conductive impurity, and the active layer 130 may have an MQW structure including an InGaN / GaN layer.

A portion of the p-type gallium nitride layer 140 and the active layer 130 are removed by mesa etching to expose a portion of the n-type gallium nitride layer 120.

A transparent conductive film 150 is formed on the p-type gallium nitride layer 140 that is not removed by the mesa etching, and a plurality of spaced predetermined intervals are formed inside the transparent conductive film 150. Intaglio irregularities 150a are formed. Here, the transparent conductive film 150 mainly consists of indium tin oxide (ITO).

The p-type electrode 170 is formed on the transparent conductive film 150.

The n-type electrode 160 is formed on a predetermined portion of the n-type gallium nitride layer 120 exposed by the mesa etching, that is, the n-type gallium nitride layer 120 on which the active layer 130 is not formed. The n-type electrode 160 and the p-type electrode 170 are preferably made of Cr / Au or the like.

According to the first embodiment of the present invention, by forming irregularities in the transparent conductive film 150, as opposed to the conventional embossed irregularities described above with reference to Figure 1, by forming the intaglio irregularities 150a as described above, The external quantum efficiency of the LED device is improved.

At this time, in the present embodiment, although the planar shape of the intaglio irregularities 150a is shown as a circle, the shape of the intaglio irregularities 150a is not limited to a circular shape but within the technical scope of the present invention, for example, a triangular shape. It may be modified in various ways, including the shape of the above polygons.

As described above, in the present invention, although the unevenness for improving the external quantum efficiency is formed in the transparent conductive film 150, the transparent conductive film 150 in the remaining region except for the uneven region (negative unevenness, 150a) is formed. Since the upper surfaces are connected to each other, the current applied from the outside through the p-type electrode 170 flows through a portion corresponding to the overall thickness from the upper surface of the transparent conductive film 150 to the lower surface, thereby providing transparent conductivity. Increasing the sheet resistance of the film 150 can be minimized. Accordingly, the present invention can prevent the operating voltage of the device from rising.

In addition, the present invention can improve the luminous efficiency of the LED device by appropriately adjusting the arrangement and size of the intaglio irregularities 150a to allow a uniform current to flow through the entire chip.

3 (a) and 3 (b) are plan views illustrating current flow control according to the arrangement of the intaglio irregularities of the gallium nitride based LED device according to the first embodiment of the present invention, and FIG. 4 is a first view of the present invention. A plan view for describing current flow control according to the size of the intaglio irregularities of the gallium nitride-based LED device according to the embodiment.

First, as shown in FIGS. 3A and 3B, the intaglio unevenness 150a is formed on at least the shortest distance (path 1) between the p-type electrode 170 and the n-type electrode 160. It is preferable to arrange.

In the case of the general transparent conductive film 150, if the thickness is constant, current is concentrated on the shortest distance (path 1) between the p-type and n-type electrodes 170 and 160 because the sheet resistance (Rs) of the layer is uniform. If the intaglio irregularities 150a are disposed on the shortest distance (path 1) between the two electrodes 170 and 160 as described above, the current concentrated in the path (path 1) is distributed to other paths (paths 2 and 3). Because you can.

As shown in FIG. 4, the size of the intaglio unevenness 150a is the outer edge of the substrate 110 from the shortest distance (path 1) between the p-type electrode 170 and the n-type electrode 160. It is desirable to get smaller and smaller as it gets richer.

In this way, by forming a sheet resistance relatively large at the shortest distance (path 1) between the p-type electrode 170 and the n-type electrode 160, the current concentrated in the path (path 1) is changed to another path (path 2). As a result, it is possible to maximize the luminous efficiency of the LED device by allowing a uniform current to flow through the chip.

On the other hand, Figure 5 (a) and (b) is a photograph showing the appearance and light emission state formed by the indentation and embossed concave-convex of the same size, Figure 5 (a) is the intaglio irregularities of the present invention is formed 5B shows a conventional relief relief.

Referring to FIG. 5, when embossed irregularities are formed, light emission is concentrated at the periphery of the electrode, whereas when embossed irregularities are formed, light emission is uniformly generated over the entire surface of the chip.

According to the first embodiment of the present invention as described above, by forming the intaglio irregularities 150a inside the transparent conductive film 150, it is possible to improve the external quantum efficiency of the device, and also to improve the electrical and optical characteristics. It can be effective.

Second Embodiment

A gallium nitride based LED device according to a second embodiment of the present invention will be described in detail with reference to FIG. 6. However, the description of the same parts as the first embodiment of the configuration of the second embodiment will be omitted, and only the configuration that is different from the second embodiment will be described in detail.

6 is a cross-sectional view showing the structure of a gallium nitride based LED device according to a second embodiment of the present invention.

As shown in FIG. 6, the gallium nitride based LED device according to the second embodiment of the present invention has the same structure as that of the gallium nitride based LED device according to the first embodiment, except that the transparent conductive film 150 is provided. Negative concavities and convexities 150a are not formed in the inside of the p-type gallium nitride layer 140, and the intaglio recesses and convexities 140a are formed in the p-type gallium nitride layer 140. The p-type gallium nitride layer 140 and the transparent conductive film ( 150 is different from the first embodiment only in that a highly doped p-type gallium nitride layer (hereinafter, referred to as a "p + gallium nitride layer", 145) is further formed.

That is, in the p-type gallium nitride layer 140 of the gallium nitride based LED device according to the second embodiment, a plurality of intaglio irregularities 140a are formed at predetermined intervals, and the p including the intaglio irregularities 140a is formed. The p + gallium nitride layer 145 and the transparent conductive film 150 are sequentially formed along the surface of the gallium nitride layer 140.

As the p + gallium nitride layer 145 is further formed, the contact area between the transparent conductive film 150 and the p-type gallium nitride layer 140 may be increased, thereby reducing the contact resistance thereof. The operating voltage can be further reduced.

As described above, the gallium nitride-based LED device according to the second embodiment of the present invention can not only obtain the same operation and effect as in the above-described first embodiment, but also further reduce the operating voltage of the device. have.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the scope of the present invention is not limited to the disclosed embodiments, but various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims also belong to the scope of the present invention.

As described above, according to the gallium nitride-based light emitting diode device according to the present invention, by forming the intaglio irregularities in the transparent conductive film or the p-type gallium nitride layer, it is possible to improve the external quantum efficiency of the device.

In addition, the present invention improves the external quantum efficiency as described above, prevents an increase in the operating voltage of the device, improves electrical characteristics, and improves the current spreading effect of the transparent conductive film, thereby making it uniform throughout the chip. Since the current can flow, there is an effect to maximize the luminous efficiency.

Claims (6)

Board; An n-type gallium nitride layer formed on the substrate; An active layer formed on a portion of the n-type gallium nitride layer; A p-type gallium nitride layer formed on the active layer; A transparent conductive film formed on the p-type gallium nitride layer and having a plurality of intaglio irregularities spaced a predetermined distance therein; A p-type electrode formed on the transparent conductive film; And An n-type electrode formed on the n-type gallium nitride layer on which the active layer is not formed; A gallium nitride-based light emitting diode device comprising a, wherein the upper surface of the transparent conductive film surrounding the intaglio irregularities are connected to each other. Board; An n-type gallium nitride layer formed on the substrate; An active layer formed on a portion of the n-type gallium nitride layer; A p-type gallium nitride layer formed on the active layer and having a plurality of intaglio irregularities spaced a predetermined distance therein; A transparent conductive film formed on the p-type gallium nitride layer; A p-type electrode formed on the transparent conductive film; And An n-type electrode formed on the n-type gallium nitride layer on which the active layer is not formed; A gallium nitride-based light emitting diode device comprising a, wherein the upper surface of the p-type gallium nitride layer surrounding the intaglio irregularities are connected to each other. The method according to claim 1 or 2, The intaglio irregularities are arranged at least on the shortest distance between the p-type electrode and the n-type electrode, characterized in that the gallium nitride-based light emitting diode device. The method according to claim 1 or 2, The size of the intaglio irregularities is smaller than the shortest distance between the p-type electrode and the n-type electrode toward the outer portion of the substrate characterized in that the gallium nitride-based light emitting diode device. The method according to claim 1 or 2, The intaglio irregularities have a planar shape of circular or polygonal gallium nitride-based light emitting diode device. The method of claim 2, And a p + type gallium nitride layer formed between the p-type gallium nitride layer and the transparent conductive film.

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